1. Field of the Invention
The invention relates in general to elevator cars, and more specifically to elevator cars in which the passenger cab has door openings in two adjacent wall portions.
2. Description of the Prior Art
Elevator systems of the traction type include a drive machine, an elevator car, and a counterweight. The elevator car and counterweight are each guided throughout their respective vertical travel paths in a hoistway of a building via guide roller assemblies mounted on the elevator car and counterweight, and guide rails in the hoistway. A safety brake on the bottom of the elevator car is arranged to be tripped by a governor upon a predetermined overspeed condition. The safety brake, when tripped, engages the elevator guide rails, and stops the elevator car.
The elevator car has a generally rectangular configuration in cross section, with the guide rails conventionally being disposed adjacent to opposite sides thereof, at the midpoints of these sides. The safety brake, which includes two safety channels or planks, extends between the guide rails, and thus its longitudinal axis is oriented perpendicular to the planes which include the side portions of the elevator car. The safety channels form part of the support structure for the elevator passenger cab.
The elevator car structure described to this point will accommodate front and rear door openings in the passenger cab. When front and side door openings in the passenger cab are specified, the conventional guide rail placement cannot be used as one of the guide rails would interfere with a side door opening. Thus, the guide rails are located at two diagonally opposite corners of the rectangular configuration of the elevator car, and the safety brake and its safety channels are oriented diagonally, relative to the passenger cab, in order to extend between the corner-mounted guide rails. This arrangement is referred to as the corner post platform and elevator car structure, because the vertical stiles which extend from the safety channels to the crosshead beam are at the corners of the elevator car.
When the safety brake assembly is diagonally oriented, the platform structure which is mounted on the safety assembly, has two unsupported corners. Thus, a much larger moment is created because of the greater distance between the corners and safety channels, than when the safety channels are in the more conventional location. In order to support these corners, and to prevent flexing of the platform, it is common prior art practice to mount two additional channels on top of the safety channels, with these additional channels being oriented between the two diagonally opposite corners which are not supported by the safety channels. This arrangement, however, adds additional weight and cost to the structure. It also adds about 10 inches to the support structure height below the floor level of the platform, necessitating a deeper pit, which in some installations may present a problem. Further, the resilient isolating pads which are used to mount the platform to the support structure must be placed at two different elevations, i.e., at the level of the first set, or safety, channel members, and at the level of the second, or additional, set of channel members. This arrangement, through localized bending of the channels, platform, and isolation pads, still results in deflection of the two corners of the platform which are not directly over the safety channels.